Description of a new genus and species of Chrysopetalidae (Annelida: Polychaeta) from the NE Atlantic, with some further records of related species

Ascensão Ravara,M Teresa Aguado,Clara F Rodrigues,Luciana Génio,Marina R Cunha

doi:10.5852/ejt.2019.539

Ascensão Ravara, M Teresa Aguado + Show 3 more

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https://doi.org/10.5852/ejt.2019.539

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Abstract

Five chrysopetalid species are reported from samples collected at bathyal depths in three NE Atlantic regions: the Bay of Biscay, the Horseshoe Abyssal Plain and the Gulf of Cadiz. Arichlidon reyssi (Katzmann et al., 1974), Dysponetus caecus (Langerhans, 1880) and D. profundus Böggemann, 2009 are free-living forms found mainly on biogenic substrates (e.g., coral and sunken wood). A brief description and taxonomical remarks are given for each of these species and their geographical distributions and habitat records were updated accordingly. Natsushima bifurcata Miura & Laubier, 1990 and Craseoschema thyasiricola gen. et sp. nov. are symbionts inhabiting the mantle cavity of chemosynthesis-based bivalves known from four mud volcanoes from the Gulf of Cadiz. Craseoschema thyasiricola gen. et sp. nov. was found inside a thyasirid bivalve and presents mixed morphological characteristics of free-living and symbiotic forms within Calamyzinae Hartmann-Schröder, 1971. A full description of the new species is given together with DNA sequences of the genes COI, 16S and H3 that were used in a phylogenetic analysis to indicate the position of the new genus within the family.

Highlights

Chrysopetalidae Ehlers, 1864 is an ecologically complex family of marine worms currently comprising more than 80 species (Read & Fauchald 2018; Watson & Faulwetter 2017), the majority of which are allocated to three subfamilies, Chrysopetalinae Ehlers, 1864, Dysponetinae Aguado et al, 2013 and Calamyzinae Hartmann-Schröder, 1971 (Aguado et al 2013)
Natsushima bifurcata Miura & Laubier, 1990 and Craseoschema thyasiricola gen. et sp. nov. are symbionts inhabiting the mantle cavity of chemosynthesis-based bivalves known from four mud volcanoes from the Gulf of Cadiz
Craseoschema thyasiricola gen. et sp. nov. was found inside a thyasirid bivalve and presents mixed morphological characteristics of free-living and symbiotic forms within Calamyzinae Hartmann-Schröder, 1971

Summary

Introduction

Chrysopetalidae Ehlers, 1864 is an ecologically complex family of marine worms currently comprising more than 80 species (Read & Fauchald 2018; Watson & Faulwetter 2017), the majority of which are allocated to three subfamilies, Chrysopetalinae Ehlers, 1864, Dysponetinae Aguado et al, 2013 and Calamyzinae Hartmann-Schröder, 1971 (Aguado et al 2013). Apart from the free-living forms, the subfamily Calamyzinae includes 21 symbiotic species (sensu Martin & Britayev 1998, 2018) of which one is an external parasite, the monotypic genus Calamyzas Arwidsson, 1932, and the others, formerly known as Nautiliniellidae Miura & Laubier, 1990, are commensals. The majority of the known commensal species are obligate symbionts living in the mantle cavity, often on the gill lamellae, of deep-sea chemosynthetic bivalves of the families Vesicomyidae Dall & Simpson, 1901, Mytilidae Rafinesque, 1815, Solemyidae Gray, 1840 and Thyasiridae Dall, 1900 (Martin & Britayev 1998, 2018; Dreyer et al 2004; Sellanes et al 2008; Aguado & Rouse 2011). In contrast with the more mobile free-living forms, symbiotic species have strongly modified neurochaetae and most of them lack notochaetae, anal cirri and jaws, as an adaptation to a symbiotic lifestyle

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